A surge arrester is used to protect relatively expensive electrical equipment from damage during periods of over-voltage in which the voltage to which the electrical equipment is exposed is higher than a normal operating range. The surge arrester diverts current around the electrical equipment to ground during periods of over-voltage, thereby shielding the electrical equipment from the high voltages and corresponding currents. Prolonged exposure to abnormally high voltages may cause the surge arrester to fail.
Conventional station class surge arresters include one or more metal oxide varistor (MOV) disks that are held in compression within a fiberglass filament wound tube between end electrodes. Current flows through the electrodes and the MOV disks during periods of over-voltage. A relatively thick filament wound tube may be needed to provide sufficient cantilever strength for station class surge arrester applications and sufficient burst strength to withstand the current associated with periods of over-voltage. For example, the walls of some conventional filament wound tubes are one to two inches thick. Consequently, such a filament wound tube requires a large amount of material to manufacture, and occupies a relatively large amount of space.
Other conventional surge arresters use hollow core technology, in which MOV disks are placed inside the hollow core of an otherwise solid structure. Hollow core technology, which provides excellent mechanical strength, normally uses pressure relief devices to vent gases formed during device failure.